A mobile station and a serving base station decide whether the mobile station performs handover or not based on channel quality of the serving base station in an IEEE (Institute of Electrical and Electronics Engineers) 802.16e network. That is, the mobile station scans neighbor cells if the channel quality of the serving base station falls below a scanning threshold for a time duration, and performs handover to a neighbor cell if channel quality of at least a neighbor cell is higher than a handover threshold for a time duration. In conclusion, performing handover or the mobile station is decided based on channel quality of serving base stations in the IEEE 802.16e network.
FIG. 1 illustrates an exemplarily of network entry process of a mobile station in an IEEE 802.16e network.
The mobile station receives downlink map (DL-MAP), downlink channel descriptor (DCD), uplink map (UL-MAP) and uplink channel descriptor (UCD) messages and acquires uplink and downlink parameters (110).
Next, the mobile station performs initial ranging and adjusts a timing offset and a power-related parameter value (111).
And, the mobile station negotiates basic capabilities with a base station (112). At step 112, the mobile station transmits the mobile station's capabilities to the base station and receives a response.
The mobile station exchanges secure keys during authorization process (113), and performs registration process with the base station (114). And the mobile station performs authentication process with a AAA (Authentication, Authorization, Accounting) server (120).
Finally, the base station transmits a Dynamic Service Addition Request (DSA-REQ) message to the mobile station to set a service flow, and the mobile station transmits a Dynamic Service Addition Response (DSA-RSP) message to the base station (122).
In an IEEE 802.16e system, a base station informs a mobile station of resource which the base station can assign to the mobile station as a percentage form using a Available DL Radio Resources parameter of a DCD message, and load balancing between the base station and the mobile station is carried out with it. Whenever the Available DL Radio Resources parameter changes, a DCD count value of DL-MAP is increased. The mobile station checks the DCD count value of DL-MAP, and if the DCD count value is different from a prior DCD count value, it judges that a DCD message was updated and reads the DCD message.
But, there is a problem that the mobile station must read the DCD message frequently to check the Available DL Radio Resources parameter because the Available DL Radio Resources parameter changes very often.